In Hoyem v. Manhattan Beach City Sch. Dist. (1978) 22 Cal.3d 508, the student and his mother sued the school district for injuries received when the student was struck by a motorcycle off the school premises but during school hours. The court held that the district could be liable as a result of negligent supervision of a student on school premises by allowing the student to leave the school grounds. The court said, "Contrary to defendant's assertion, no California decision suggests that when a school district fails to properly supervise a student on school premises, the district can automatically escape liability simply because the student's ultimate injury occurs off school property." (Id. at p. 516.) The court said that Education Code section 44808 does not limit "a school district's responsibility to supervise students during school hours on school premises." (Id. at p. 518.) The court in Hoyem, supra, 22 Cal.3d at page 517, stated, "Although the initial portion of the statute provides that 'no school district shall be responsible . . . for the conduct or safety of any pupil . . . at any time when such pupil is not on school property,' the section goes on explicitly to withdraw this grant of immunity whenever the school district, inter alia, 'has failed to exercise reasonable care under the circumstances.'" In Hoyem v. Manhattan Beach City Sch. Dist., a 10-year-old boy who was enrolled in summer school left the school campus prior to the end of the summer school day and was struck and injured by a motorcycle at a public intersection. He sued the school district alleging the accident and his injuries were proximately caused by school authorities' negligent supervision of students. Finding that the defendant school district incurred no liability as a matter of law, the trial court sustained the school district's demurrer, dismissed the suit, and entered judgment in the defendant's favor. The Supreme Court reversed and held that if the truant student could prove that his injuries were proximately caused by the school district's alleged negligent supervision, the district could be held liable for the damages resulting from the child's injuries, with liability diminished on the basis of comparative negligence principles to the extent the trier of fact would find that the student's own negligence was a proximate cause of his injuries. (Id. at pp. 512, 519, fn. 4.) The liability of the motorcycle driver was not at issue in the appeal, as it was addressed in a separate suit filed by the student, but the Hoyem court observed that the school district could join the driver, as a cross-defendant in the plaintiff's suit against the district, to pursue a comparative indemnity claim. (Id. at pp. 512, fn. 1, 521.) The Hoyem court stated the school district had a "firmly established duty to exercise due care in supervising [the plaintiff] while he was on school premises." (Hoyem, supra, 22 Cal.3d at p. 515.) The court rejected the district's argument that if a school district may be liable for injuries to a truant, it would require school districts to construct "truant-proof" schools. The court said that a school district's duty only requires "ordinary care" such that schools are "reasonably supervised." (Id. at p. 519.) In Hoyem, the court rejected the school district's assertion that the conduct of the motorcycle driver who hit the truant plaintiff student was a superseding cause cutting off any liability the district might have for the accident. (Hoyem, supra, 22 Cal.3d at p. 521.) In short, a 10-year-old boy was injured after leaving the school campus without permission. The court held the school district was not exonerated from liability as a matter of law for claims that it negligently supervised the child on school grounds. The court relied on former title 5 of the California Administrative Code, section 303, which provided: " 'A pupil may not leave the school premises at recess, or at any other time before the regular hour for closing school, except in case of emergency, or with the approval of the principal of the school.' " ( Hoyem, supra, at p. 514; Cal. Code Regs., tit. 5, 303.) The court explained it "had no doubt that this rule is at least in part for the pupils' protection, and that the school authorities therefore bore the duty to exercise ordinary care to enforce the rule." ( Hoyem, supra, at p. 514.) The court addressed the question of "whether, under California law, a school district may ever be held liable when, as a result of school authorities' negligent supervision of students on school premises, a pupil leaves the school grounds during school hours and is subsequently injured by a motorist." (Id. at pp. 511-512.) In answering that question in the affirmative, the court stated: "Our cases have long established that a school district bears a legal duty to exercise reasonable care in supervising students in its charge and may be held liable for injuries proximately caused by the failure to exercise such care." (Id. at p. 513.) " 'We entrust the safety of our children to our public school authorities during school hours. They are bound to exercise an amount of care for their safety during that period commensurate with the immaturity of their charges and the importance of their trust.' " (Id. at pp. 519-520.) The court rejected the school district's argument that the conduct of the motorcyclist who hit the plaintiff constituted a superseding cause, precluding any liability on the part of the school district: "Neither the mere involvement of a third party nor that party's wrongful conduct is sufficient in itself to absolve the defendants of liability, once a negligent failure to provide adequate supervision is shown. ...' " (Id. at p. 521.)